YAP1

YAP1 (Yes-associated protein 1), also known as YAP or YAP65, was first identified by virtue of its ability to associate with the SH3 domain of Yes and Src protein-tyrosine kinases. YAP1 is a potent oncogene, which is amplified in various human cancers, and it is one of the two main effectors of the Hippo tumor suppressor pathway.

Modular Structure of YAP1 Protein

Cloning of the YAP1 gene facilitated the identification of a modular protein domain, known as the WW domain. Two splice isoforms of the YAP1 gene product were initially identified, named YAP1-1 and YAP1-2, which differed by the presence of an extra 38 amino acids that encoded the WW domain. Apart from the WW domain, the modular structure of YAP1 contains a proline-rich region at the very amino terminus, which is followed by a TID (TEAD transcription factor interacting domain). Next, following a single WW domain, which is present in the YAP1-1 isoform, and two WW domains, which are present in the YAP1-2 isoform, there is the SH3-BM (Src Homology 3 binding motif). Following the SH3-BM is a TAD (transcription activation domain) and a PDZ domain-binding motif (PDZ-BM) (Figure 1).